U.S. patent number 3,746,780 [Application Number 05/118,904] was granted by the patent office on 1973-07-17 for video display system.
This patent grant is currently assigned to The Mitre Corporation. Invention is credited to Rollin P. Mayer, Kenneth J. Stetten.
United States Patent |
3,746,780 |
Stetten , et al. |
July 17, 1973 |
**Please see images for:
( Certificate of Correction ) ** |
VIDEO DISPLAY SYSTEM
Abstract
A video information transfer and display system having a
plurality of video display devices and apparatus to select for
display at particular display devices, on the basis of
identification data incorporated within the video signals,
predetermined video display information from sequential video
signals also received at many other display sites. Video recorders
are adapted to record selected portions of commercial
television-type video signals and maintain the image displayed on
associated television receivers.
Inventors: |
Stetten; Kenneth J. (Reston,
VA), Mayer; Rollin P. (Arlington, VA) |
Assignee: |
The Mitre Corporation (Bedford,
MA)
|
Family
ID: |
22381446 |
Appl.
No.: |
05/118,904 |
Filed: |
February 25, 1971 |
Current U.S.
Class: |
386/239;
348/E7.071; 379/93.26; 725/100; 725/97; 725/93; 379/102.03;
345/10 |
Current CPC
Class: |
H04N
21/812 (20130101); H04N 1/00098 (20130101); H04N
7/17318 (20130101); H04N 2007/1739 (20130101) |
Current International
Class: |
H04N
7/173 (20060101); H04N 1/00 (20060101); H04N
1/21 (20060101); H04N 7/16 (20060101); G11b
027/10 (); G11b 031/00 (); H04n 005/78 () |
Field of
Search: |
;178/6.6A,6.6DD,6.7R,DIG.13,DIG.23 ;340/324A ;179/2TV |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Britton; Howard W.
Claims
Having thus described our invention, we claim:
1. A video information transfer system comprising video display
means,
means to receive signals for display by said video display
means,
means to identify particular portions of said received signals,
means to record signals received by said signal receiving
means,
means activating said recording means during receipt of said
identified signal portions,
said activated recording means then recording the identified
portion of the received video signals,
and means utilizing said recorded portion to maintain on said video
display the information contained within said identified signal
portion,
said identification means comprising at least first and second
portions,
said second portions serving to control functions associated with
particular ones of said video display means,
one of said first portions of the identification means comprising a
primary identification means and an associated keying means,
means for retaining said keying means for comparison with
subsequently sent second portions,
and means activating said controlled function upon receipt of a
second portion corresponding to said retained keying means.
2. A video information transfer system comprising video display
means,
means to receive signals for display by said video display
means,
means to identify particular portions of said received signals,
means to record signals received by said signal receiving
means,
means activating said recording means during receipt of said
identified signal portions,
said activated recording means then recording the identified
portion of the received video signals,
means utilizing said recorded portion to maintain on said video
display the information contained within said identified signal
portion,
means associated with at least one identification means for
originating and sending a user-originated video display to a video
recording means,
means responsive to said identification means for initiating the
sending of at least a part of the video frame from said
user-originated means,
and means for routing said user-originated video frame to any
required intermediate and final video recording means.
Description
Conventional visual display systems are subject to several
limitations. In all presently existing systems a sacrifice has been
made in either simplicity of display apparatus or in system
flexibility and performance. For example, ordinary commercial
television receivers provide satisfactory display upon the TV
screen of a cathode ray tube at reasonable costs. On the other
hand, every receiver tuned to a given channel containing video
information receives and responds to identical video information
and thus presents on its TV screen a display identical to that on
every other receiver tuned to the same channel. On the other hand,
systems permitting selected predetermined displays at particular
sites have involved complex specialized equipment. PLATO, a system
being developed by the University of Illonois, provides different
displays for different users but requires complex
digitally-controlled display devices currently under
development.
There have been attempts to provide different displays at different
sites with simple display devices such as television-type displays.
These systems operate with the desired visual information
prerecorded on magnetic tape or other recording means. In such
systems a given tape or tape cassette contains the video
information for a particular display sequence. While such systems
do permit different displays at different user locations, they do
not provide flexibility in the material displayed, nor do they
permit interaction between the viewer and the system. Rather the
viewer is constrained to the particular sequence of displays
dictated by the totality of the video information recorded on the
particular tape or cassette which is being used with that site. In
other words, the only choices available to a user are choices
between those specific prerecorded tapes physically available to
him.
A somewhat similar choice "in bulk" of video information is
provided by systems providing for switching between various video
channels. A viewer may be able to pick among several channels, but
he, and everyone else viewing a TV screen presenting video
information carried by that channel, is contrained to the
information being transmitted over that channel.
Particularly for certain defense-oriented systems where the user's
needs can be particularly well defined so that special purpose
systems are suitable, there have been some high-cost data-link
systems permitting particular displays at particular receiving
sites. These systems normally involve specially coded transmission
signals and special purpose display devices. These devices may be
storage-type display apparatus giving stylized displays adapted to
the particular mission involved. Thus these systems do not solve
the problem created by the conflict between low cost and system
simplicity versus system performance and flexibility but rather go
to high-cost special purpose equipment throughout. Such systems are
too costly for educational or other general use display systems in
which large numbers of receiving sites must be provided at minimal
cost.
Accordingly it is an object of the present invention to permit the
display of particular display information addressed for receipt at
particular display sites using conventional video display devices
and conventional video transmission systems.
Another object is to permit users to select for viewing particular
desired displays from many displays transmitted over a single video
channel.
Another object is to permit individually selected and adapted
displays at many sites through the use of commercially available
video equipment with a minimum of special purpose identification
and display control apparatus.
A further object is to achieve maximum flexibility and user-system
interaction without significantly increasing system cost.
A still further objective it to provide picturephone and document
delivery capabilities.
These and other objects are achieved by utilizing conventional
video display devices such as the TV screen on the cathode ray tube
of a conventional TV receiver and conventional video-tape
recorders. The video signals for a particular screen are maintained
by recorded video information, the video signals recorded at a
particular location being controlled by identification information
within otherwise conventional sequential television video signals.
The identification information permits individual ones of many
television receivers to display on their screens individually
adapted, and different, displays from a commonly received,
sequential video television signal.
REFERRING NOW TO THE DRAWINGS:
FIG. 1 is a block diagram of an over-all information transfer and
display system with user feed-back via telephone communication;
FIG. 2 shows circuit modifications to adapt a commercial television
cassette recorder for use with the present invention;
FIG. 3 gives signal waveforms for a coded identification
address;
FIG. 4 shows circuitry appropriate to decode addresses at a
particular user site;
FIG. 5 is a block diagram of a system wherein a multiple level or
cascaded address is used to provide both two addresses and
additional function control;
FIG. 6 is a block diagram of a neighborhood picture-phone
system;
FIG. 7 is a block diagram of an expanded picture-phone system;
and
FIG. 8 is a block diagram of a mail delivery system.
The over-all system for one mode of operation is illustrated in
FIG. 1. Television screen 2 is a conventional television cathode
ray tube display screen with associated conventional television
video circuitry. The subscriber or user 4 observes the image
displayed upon screen 2.
By way of illustration, it will be assumed that the subscriber has
subscribed to a weather service available from the transmission
system. He would now like to see the forecast for northern New
England, since he is planning a skiing trip. Accordingly, he turns
on his display equipment, described below, and uses his telephone
to dial first the television display system to which he has
subscribed and, second, the code number for weather information. A
conventional telephone 6, preferably the touch-tone version, with
conventional telephone company central-station switching 8,
provides a telephone dial signal input 10 received by a computer
installation 12 serving to control the operation of the system.
In this example there are 10 different services available and the
number for the weather service is 5. Accordingly, the number 5 will
be received by the computer as a new request. In addition, the
subscriber will send a signal identifying him, in this example
display location 11. Conventional software, indicated by block 14,
reads the received digital information and provides a number for
the display frame address over line 16 and for the user address
over line 18.
This software is analogous to that used in time-shared commercial
services provided by central computing installations to many users
via telephone lines. In such systems information fed in over
telephone lines is subjected to predetermined computer processing.
For that processing, a given program to perform the desired
function, such as entering payments to a particular count, is
chosen. In an analogous manner the digital information representing
the desired display which has been transmitted by the user in the
present invention is subjected to software processing indicated by
block 20. In this case rather than selecting a particular program
for the processing of the user's data particular digital input
information is identified with particular frame addresses and
stored video information. In a manner analogous to the retrieval of
a particular stored program from computer memory, the programming
of block 22 utilizes the particular frame address, supplied over
line 24, to control the retrieval of the desired display frame from
the storage means, block 30.
While a single block 30 is shown, the system employs conventional
recording means with associated controls to make available the
video information for many different frames on demand. Any
conventional video storage means can be employed, as for example, a
video disc recorder. If a video disc recorder is being used, the
general weather display information is recorded on a particular
track of one disc of that recorder, for example, on track 26.
Accordingly the operation of the software blocks 20 and 22 will
serve to select track 26 when number 5 is dialed. The information
on video disc track 26 is then read to the TV transmitter 32. At
the start of read-out of this track, the video disc initiates the
program in software block 28, using conventional methods of
synchronizing software with external equipment. Block 28 has
previously been prepared for this activity by software block 21,
which has supplied the subscriber's TV address that is to be
encoded upon the stored signal. If desired, the user can dial his
location number, 11 for example. In either case, utilizing software
analogous to that employed to determined user addressing for a
time-shared central processing system the user's telephone number,
or location number, is converted into a TV address by use of the
active line table in block 21. Suitable codes and decoding
mechanisms will be discussed subsequently in connection with FIGS.
3 and 4. When software block 28 is thus initiated, it sends the
required coded address to the TV transmitter for transmission.
Thus, TV transmitter 32 receives for transmission first the coded
address from block 28 and then the video frame from block 30. This
transmitter then transmits, via air, cable or any other
conventional transmission media, a video television signal to the
subscriber's television receiver 34. The composite video signal is
fed through lines 36 and 38 to a video recorder 40 and an address
detector 42, respectively. The address detector also receives the
horizontal sync signal through line 44. When the address of the
subscriber's display location 11 is received, a WRITE + signal is
delivered to the video recorder 40 over line 41 and the recorder
proceeds to record the general weather forecast which has been
requested by subscriber 4. The user's video recorder may be a tape
cassette, reel-to-reel, or other recorder having the ability to
play back single frames, -- the so-called "stop-frame" mode, and to
record. After recording, the composite video portraying the general
weather forecast is sent from the recorder over line 43 to the
conventional video circuits controlling the display on the user's
television screen 2. As will be discussed in greater detail below,
the video recorder 40 repetitively sends the stored frame at the
conventional television frame and field rates to maintain the
desired display on TV screen 2.
In the example being utilized the subscriber wanted the northern
New England forecast. The general weather forecast display contains
a list of several text lines giving code numbers the user can dial
to obtain more specific weather forecast displays for various
areas. Therefore, the subscriber now dials again, giving the number
for northern New England and the more detailed display for that
particular region is delivered to the subscriber exactly as the
general weather display had been processed. The only difference is
that a different code number is utilized so that the video
information stored on a different track of the video disc is
delivered to the subscriber, as determined by software block 20,
which uses conventional table and coding techniques to match the
customer's present code number with his new request number to
derive the new desired track number.
If every individual subscriber on the average would like a
different display as often as every ten seconds, displays with full
television frame detail can be delivered to three hundred different
subscribers over a single television channel. This result is
obtained by multiplying the number of television frames per second
in a conventional transmission, 30, times the number of seconds,
10, to give the number 300.
A conventional television frame is composed of two fields, each
field containing one-half of the lines of the television picture,
alternate lines appearing in each field. If the detail required is
not greater than that given by a single field, twice the number of
subscribers can be handled with the same frequency of display
change. Blank lines of the screen can be avoided merely by making
each line for the missing field identical to the preceding line
from the transmitted field, as is commonly done in stop-frame
playback from conventional video tape recorders.
FIG. 2 sets forth in block diagram form circuitry appropriate for a
video tape recorder modified to be useful in the system of the
present invention. Conventional circuitry for normal operation is
not shown, including circuitry for synchronizing the heads to the
incoming signal, other controls for normal operation, and so forth.
If the synchronization of the heads to the incoming signal is
maintained even while the output of the tape recorder is the
recorded signal rather than the incoming signal, the incoming
signal to be recorded in response to control signals to be
described below will already find the heads synchronized properly.
If the four switches which have been added to a normal video tape
recorder, switches Sw2A, Sw2B, Sw2C and Sw2D, are in the right-hand
or "normal" position, the recorder functions in its normal
unmodified manner. In this mode switch Sw1A supplies power to the
recording oscillator 50 and the recording amplifier 52 or to the
playback amplifier 54, depending upon the switch position. As shown
in FIG. 2, the switches are set for the recording mode. Thus power
is supplied to the recording oscillator 50 and the recording
amplifier 52 but not to the playback amplifier 54. Sw1B connects
the recording heads 56 to the recording amplifier but not to the
playback amplifier. Sw1C does not connect the playback amplifier to
the FM detector 58 but does connect the FM detector 58 to the
recording oscillator 50 so that the video input may be
monitored.
With the additional manual switch, Sw2A, B, C, D, in the "special"
position for use with the present invention Sw2A applies power to
both the recording amplifier 52 and the playback amplifier 54. Sw2B
connects the recording heads 56 to both the recording amplifier 52
and the playback amplifier 54. Sw2C connects the FM detector 58 to
only the playback amplifier 54. Sw2D connects the recording
oscillator 50 to a conventional inverter 60 serving as a control
circuit for the present invention. This control circuit is
activated by a "WRITE +" signal on line 62.
In the absence of a WRITE + signal the line 62 is at ground level
signifying a "READ" operation. With a ground level input the output
of the inverter 60 to Sw2D is positive, typically 4 volts. This
positive voltage is applied through resistor R1 to recording
oscillator 50 to place the oscillator in an inoperative state. This
operation may be achieved in any conventional manner, for example,
by raising the voltage level of the emitters of the recording
oscillator to cut off its transistors. With the recording
oscillator cut off there is no input to the recording amplifier 52
and no output from the recording amplifier 52 to the recording
heads 56.
In the special mode Sw2B connects the playback amplifier as well as
the recording amplifier to the recording heads 56 so that the
recording heads will play back the frame recorded, if any, on the
section of tape being traversed by the heads. A resistor diode
network comprising R2 and the diodes D1 and D2 has been added to
the input side of the playback amplifier 54 and causes negligible
attenuation of the weak playback signal. Thus the playback of the
recorded frame occurs in the conventional manner.
When the WRITE + signal is applied to the control inverter 60, the
input of the inverter is raised, typically to plus 4 volts. The
output of the inverter is then at ground level so that the
recording oscillator is connected through R1 to ground and
functions normally in the manner of an unmodified video tape
recorder. With the recording oscillator 50 functioning, the
incoming video signal over line 64 is recorded, the recording
operation through recording heads 56 occurring in the conventional
video tape recorder manner. The resistor diode clipping circuit
formed by resistor R2 and diodes D1 and D2 serves to greatly
attenuate the strong signal being applied to the recording heads 56
so that the signal applied to playback amplifier 54 is comparable
in strength to the signal normally received on playback from the
recording tape through recording heads 56. Therefore, this signal
may safely be applied to the playback amplifier 54. The output from
the playback amplifier 54 is applied through Sw2C to FM detector 58
to permit the immediate display of the video signal being
received.
If the user desires to save the recorded video information for
later use, the tape may be advanced manually, or automatically,
before recording different video information. Similarly, periodic
advancement of the tape may be desirable to minimize wear of the
magnetic tape which might otherwise be caused by motion of the
recording heads.
Since the action of the inverter 60 controlling the operation of
the recording oscillator is under electronic control, depending
upon the present or absence of a WRITE + signal on line 62,
recording may be initiated and terminated at will. For example, if
conventional television video is being transmitted, that is video
with thirty frames per second, each frame being composed of two
interlaced fields, the WRITE + signal may be turned on and off at
any number of places during the transmission of a single frame.
Therefore, if desired, only a predetermined group of the lines
composing a field of video information may be recorded. If it is
anticipated that users will often wish a given duration of
recording, duration control 69 may be added to the WRITE + input.
This circuitry consists of a conventional latch circuit designed to
turn off the WRITE + signal when one vertical synchronization
signal has occurred if recording of a single field is desirable, or
when two vertical synchronization signals have been received if a
full frame of recording is desired.
If the recording head synchronization circuits in the video
recorder are accurate enough to maintain horizontal sync coherence,
as is normally the case with studio or high quality units,
recording may be started and stopped at any line on the screen
without destroying the lines above or below. Otherwise, horizontal
synchronization will be disturbed whenever a switching occurs, and
it will be more satisfactory in some applications to switch only at
the top or bottom of the screen.
FIG. 3 shows coded waveforms suitable for use in the present
invention. The waveform of one line of television video is shown at
a in FIG. 3. The first 8 microseconds of the picture line, which is
about 52 microseconds of picture data between sync pulses, is
divided into ten segments, each 0.8 microseconds long. Each segment
is thus more than six picture-elements wide, and the maximum
frequency is the reciprocal of a two-segment period, or 625
kilohertz, a frequency which is well within the bandwidth of
conventional TV transmitters and receivers. Each segment serves to
transmit one bit of identification data and is either at the
picture black level, (which is a higher amplitude of carrier
modulation in U.S. standards), or at the picture white level,
(lower amplitude). The first two bits of the 10 segments serve as a
control flag, and the remaining eight bits are coded to transmit
the identification data. The two bits of the control flag are coded
white-black as shown in waveform a of FIG. 3. Therefore, every
picture line that is not to be an address code can begin with the
first 1.6 microseconds all black or all white so that picture
display information will not be mistakenly utilized as
identification data. The effect of treating the first 1.6
microseconds in this manner is to produce a 3 percent left margin,
a margin which is normally off the screen in any event. Thus any
line of any field of television video information may be identified
as an address control line simply by transmitting a control flag
and code data on that line. The remaining waveforms shown in FIG. 3
are utilized in conjunction with the description of the circuit of
FIG. 4.
FIG. 4 shows circuitry appropriate to decode addresses in the
system of the present invention. The NAND circuits, inverters and
flip-flops used in this circuit are conventional ones such as those
found in integrated circuit flip-flops SN74107, inverters SN7404,
NAND gates SN7400, eight-input NAND gates SN7430 and AND/OR
comparator integrated circuits SN7451 produced by Texas
Instruments, Inc. or their equivalents. Also used is a single-shot
(or one-shot) mono-stable multivibrator labelled 74121 S.S. which
is the integrated circuit No. SN74121 produced by Texas
Instruments, Inc. or its equivalent. Such multivibrators can be
installed and adjusted to provide any of a wide variety of
pulse-width outputs (30 nanoseconds or more) in response to an
appropriate input.
The front end of the TV receiver 34 supplies two conventional
signals to the following portions of the circuit of FIG. 4: a
horizontal sync pulse over line 44 and a composite video signal
over line 38. In this example, the voltage levels are 4 volts
positive for black video signal and 0 volts for white video picture
signal. A low-pass filter R10C10minimizes noise transients while
providing reasonable transient response during the address control
signal. Inverter 72 serves as a buffer and wave shaper to deliver a
digital signal of standard form to the remainder of the circuit.
This digital signal closely follows the bit pattern transmitted as
the control flag and address code.
The horizontal sync pulse on line 44 is fed to input B of
single-shot multivibrator 74. Since the input A of multivibrator 74
is grounded, the multivibrator will fire when the pulse on input B
becomes positive. At that time, its output Q will go low and remain
low for the time period for which the single-shot multivibrator 74
has been adjusted, as shown on waveform b of FIG. 3. This low
output on line 76 is fed to the B input of single-shot
multivibrator 78. Thus the output of multivibrator 78, which also
has its A input grounded, will go high on line 80 at the end of the
Q signal on line 76, and stay high for a period equal to the period
for which single-shot multivibrator 78 has been adjusted, as shown
on waveform c of FIG. 3.
The function of single-shots 74 and 78 is to provide signals
indicative of when to sense for the transient from white to black
of the control flag waveform shown in waveform a of FIG. 3. The
period of single-shot 74 is adjusted to control the beginning of
the sensing operation, this control being provided by the start of
the high-level pulse on line 80. The period of single-shot 78 is
adjusted to control the end of the sensing operation, this control
being provided by the end of the high-level pulse on line 80. This
signal over line 80 is applied to the clear (reset) input of
flip-flop 84. Thus flip-flop 84 is forced to 0 at all times except
when sensing is to occur as permitted by the signal over line 80
from the Q output of single-shot 78. The output from inverter 72 is
fed over line 86 to flip-flop 84. If a white-to-black transient, a
down transient on line 86, occurs during the interval that
flip-flop 84 is operative for sensing, the KJ input terminals,
supplied by fixed ground and positive inputs respectively, are
clocked into the flip-flop 84 and its output is at the ONE
condition until line 80 again goes low. The waveform at the output
of flip-flop 84 (on line 87), when a control flag has occurred, is
shown as waveform d in FIG. 3.
If flip-flop 84 detects a control flag, and, therefore, momentarily
contains a ONE, the following activity occurs. The zero side of
flip-flop 84 connected to line 88 momentarily goes down to the zero
level and, therefore, resets all the flip-flops in the shift
register 90 and resets flip-flop 92 since their reset terminals are
connected to the zero output of flip-flop 84 over line 88. When
flip-flop 92 is reset, its output, the WRITE + signal on line 41,
goes to zero. Therefore, writing as shown in FIG. 2 stops so that
the recorder 40 will not record the address code bits. Thus address
code bits are not visible on the user's TV screen.
When the first flip-flop of shift register 90, flip-flop 96, is
reset by the output from flip-flop 84, it initiates receipt of the
address code, serving as a start-stop control for the shift
register. Flip-flop 96 is turned on, --set to zero, by the reset
pulse from line 88. Flip-flop 96 remains set to zero while the
contents of flip-flops 98, 100 and 102 (but not 104) are
successively shifted into it as described below, because these
flip-flops have been reset to zero by the signal from flip-flop 84.
For circuit simplicity only flip-flops for four bits are shown,
although for the code of FIG. 3 four additional flip-flops
identically connected in series are required. Flip-flop 96 is
turned off, --set to ONE, when the contents of flip-flop 104 is
finally shifted into it, because flip-flop 104 has been reset to
ONE by the signal from flip-flop
The zero side of flip-flop 96 is connected to NAND gate 206. Since
flip-flop 96 is normally off, this input to NAND gate 106 is
normally low, and consequently the output of inverter 108 is
normally low. A high output from inverter 108 is the enabling
signal for a conventional oscillator consisting of single-shot
multivibrators 110 and 112 and inverter 114. However, since
inverter 108 is low, the oscillator is not active, and both Q
outputs from the multivibrators 110 and 112 are low. Now when
flip-flop 96 goes "on" as a result of flip-flop 84 having detected
a control flag, it would "enable" the oscillator 109, except that
this enabling is temporarily inhibited by the other input to NAND
gate 106 coming from the Q of multivibrator 78. Single-shot
multivibrator 78, in addition to controlling the period for sensing
the control flag, thus also controls the starting of the oscillator
109. Therefore, single-shot 78 has its period adjusted so that, in
conjunction with the timing of single-shot 74 and the horizontal
sync signal, it will turn off its "Q" output (and thus turn on its
Q output) at approximately the center of the second bit position of
the control flag. Turning on the Q output of single-shot 78, will
enable the oscillator 109 and oscillator 109 will then sense the
approximate center of the succeeding bit positions of the address
as described below.
Thus the oscillator 109 will be enabled at the center of the second
flag bit if a flag has occurred. Since single-shot 78 will not be
triggered again during the receipt of the address bits, the
oscillator 109 will remain enabled until the flip-flop 96 is turned
off.
The oscillator 109 is a conventional circuit for single-shot
multivibrators such as the SN74121 integrated circuits. The
operation is as follows. Single-shot multivibrators 110 and 112
each fire when their A and B inputs first become low and high,
respectively. When inverter 108 inhibits the oscillator, it does so
by holding the B input to single-shot 110 low thus inhibiting the
start of a new output from single-shot 110, and via inverter 114
holding the A input of single-shot 112 high thus inhibiting the
start of a new output from single shot 112. Conversely, when
inverter 108 enables the oscillator, it does so by holding these
same two inputs in their "on" position continuously, thus allowing
the other two inputs, A of single-shot 110 and B of single-shot
112, to function.
In the quiescent state, both single-shot 110 and single-shot 112,
are "off" . That is, their Q outputs are low, and their Q outputs
are high. Because the Q of single-shot 112 is connected to A of
single-shot 110, single-shot 110 is ready to fire as soon as
inverter 108 enables it. Because Q of single-shot 110 is connected
to B of single-shot 112, single-shot 112 is ready to fire as soon
as inverter 114 enables it, but one purpose of inverter 114 is to
delay the enabling signal very briefly until single-shot 110 has
fired, thus shutting off B of single-shot 112 so that single-shot
112 does not fire immediately, but waits until the period of
single-shot 110 is over. Because of these interconnections,
single-shot 110 fires first. When its period is over and it
expires, it fires single-shot 112. When single-shot 112 expires, it
fires single-shot 110 and so on, until the enabling signal from
inverter 108 is turned off, so that the subsequent expiration of
single-shot 110 (which will be on at that time, as discussed below)
will not fire single-shot 112 and both single-shots remain off.
Waveforms e and f of FIG. 3 show the waveforms at the Q outputs of
single-shots 110 and 112.
The period of single-shot 112 is adjusted to be very short,
typically 30 nanoseconds, so that it can be used to sense only a
specific short position of the video input. The period of
single-shot 110 is adjusted so that the sum of the periods of the
two single-shots, in other words the over-all period of the
oscillator 109, is the same as the bit period of the address bits
on the incoming video signal. Thus, since single-shot 78 is
adjusted as described above to start the oscillator in the center
of the second bit position of the control flag, the first 30
nanosecond pulse and succeeding pulses from single-shot 112 will
occur in the center of succeeding bit positions of the address.
Flip-flops 96, 98, 100, 102 and 104 are connected as a conventional
shift register. (As noted above, four flip-flops have been omitted
from the drawing for circuit simplicity). Each pulse from
single-shot 112 Q output is fed to inverters 116 and 118 in series.
Inverters 116 and 118 serve to provide isolation and supply the
driving pulses for the shift register 90.
Each successive pulse from inverter 118 shifts the bits in the
shift register one place to the left, and at flip-flop 104, senses
the current address bit of the incoming video signal (which appears
at inverter 72 in positive form, and at inverter 120, fed by
inverter 72, in complement form) and copies that incoming address
bit into flip-flop 104. Thus at the end of the first shift pulse
from single-shot 112, the first bit of the address appears in
flip-flop 104, flip-flop 102 contains the one bit that will
subsequently be shifted into flip-flop 96 to turn off the
oscillator, and the remaining flip-flops all contain zero. At the
end of the eighth shift pulse from single-shot 112 (the fourth
shift pulse for the circuit as drawn with four flip-flops omitted),
the eighth bit of the address appears in flip-flop 104 and the
other bits of the address have been shifted into the corresponding
adjoining flip-flops. Flip-flop 96 will have just received the ONE,
thus disabling the oscillator, which will become quiescent as soon
as single-shot 110 expires, and no further shifting or sensing
occurs.
The outputs from the flip-flops of the shift register 90 along with
corresponding outputs from selection switches S1 through S8 are
connected to the comparison circuitry 125 consisting of 7451
comparison circuits 122, 124, 126 and 128, and the eight-input NAND
gate 130. The switches are set to the address identification code
of the particular user.
While shown as simple two-position manual switches connecting one
of two comparison circuit terminals to ground, the switches may
take any of a number of other forms. Some such forms are: They may
be permanently wired connections to the subscriber's TV set and the
computer can consult a table that relates the subscriber's name or
security code with his coded address number. They may be contacts
on a rotary switch that the subscriber may set to any number which
he is told to use, or the subscriber may dial any of several
publicly listed numbers for receiving publicly broadcast coded
frames. They may be electronically controlled by means such as
those currently being described, permitting the computer of the
system of FIG. 1 to send a primary coded address, detected by
manual switches, followed by a "key number" that is used to set the
electronic address switches. Thus many subscribers can have their
electronic switches automatically set to the same key number, and,
therefore, the computer can use this key number as a subservient
coded address to transmit a given often-used frame only once to all
these subscribers. In a similar manner, the computer could transmit
a sequence of commonly used frames at regular intervals identified
by subservient coded addresses, and then send the subscriber's
primary code and the key required to set the subscriber's
electronic address switch to receive the required one of these
common frames, or to receive a specially prepared frame. In this
manner, 500 subscribers, for example, could be controlled during
just one frame time in which 500 flagged address lines containing
keys are sent during 1/30 of a second.
In accordance with the conventional operation of the comparison
circuit, if each of the switches S1 through S8 matches the
corresponding address bit in the flip-flops of shift register 90,
then each input to NAND circuit 130 will be high and the low output
of NAND circuit 130 will indicate an exact match. Otherwise, at
least one flip-flop will not match the corresponding switch, and
the high output of NAND circuit 130 will indicate disagreement or
mismatch. Thus, because of inverter 132, the J input of flip-flop
92 will be high only if the received coded address, as stored in
the shift register 90, agrees with the desired address as
represented by the selection switches. Thus a WRITE + pulse will
subsequently be delivered to line 41 only when there is an address
match, as described below.
As described above, flip-flop 92 was reset to zero by the detection
of a control flag. It will remain reset until the occurrence of the
next horizontal sync pulse from line 44 which is applied to its
clock input over line 134. At this time, if the previously received
address is the desired address, the J input to flip-flop 92 will be
high and the horizontal sync pulse will clock flip-flop 92 to a
ONE, thus turning on the WRITE + signal, to initiate recording the
desired display information. Succeeding horizontal sync pulses will
not disturb flip-flop 92 because the K input is permanently off and
the state of the J input is immaterial because flip-flop 92 will
either remain undisturbed, if J is also off, or will remain ONE if
J is high.
Consequently, when the subscriber's address is received, writing
will start at the beginning of the next horizontal line, and
writing will continue until a new address is sent, as signaled by
its control flag, at which time writing will stop. If the new
address is not for the subscriber, then wiring will not be resumed.
No further writing will occur unless either a coded address is
received which matches the address of the address selection
switches, or the address selection switches are changed to match
the last received address stored in shift register 90.
Any conventional method of transmitting the encoded enabling signal
from its source to the subscriber's recorder may be employed.
Moreover, this control signal can be employed in conjunction with
any video line available to a given display site so that specific
TV frames, or portions of frames can be recorded in response to
these control signals. These operating modes permit either the
user, or sender, or both to exercise partial or complete control
over the manner in which the control signals will be used to select
some frames, or portions of frames for display, and reject others,
if any.
Thus although the described example makes use of a binary coded
subscriber address, sent as an 8-microsecond part of the TV video
signal, the system could use other control signals, such as signals
sent separately from the TV signal, as, for example, over telephone
lines to the subscriber or user, or be based upon the selection of
one or more of a set of sequentially ordered frames counted or
timed from a reference signal sent from the source, or available to
both the source and the receiver. Address codes could be
transmitted at any fixed or specified bit rate during any portion
of the TV frame, or sent, for example, on a different carrier or
subcarrier, and encoded in binary or other code mechanisms. While a
single address mode has been described in detail, cascaded
addresses could be used to allow a subscriber's equipment to
capture a subsidiary control signal which is then used to control
signal recording or to perform some additional function.
FIG. 5 illustrates a system wherein a multiple level or cascaded
address is used to provide both two addresses and additional
function control. In the system of FIG. 5, address bit distributor
136 separates the portion of the multiple-level address into three
component parts. These component parts, that is the bit signals
comprising the respective portions of the cascaded address, are fed
respectively to generic address detector 138, specific address
detector 140, and additional function detector 142. These detectors
function in a manner analogous to that described in connection with
the circuit of FIG. 4, each working on its respective portion of
the cascaded signal. The address bit distributor 136 can comprise
any conventional method of distributing portions of a signal, as,
for example, a shift register with the stages comprising each of
three successive portions of the shift register being fed to the
respective detectors.
If either the generic detector 138 or the specific address detector
140 indicates a match, the video recorder 40 will be enabled. If
additional function detector 142 indicates a match, then the
equipment controlled by that detector will be enabled. In the
example of FIG. 5, the additional function is the operation of TV
camera 144. Thus, for example, when the sub-address appropriate to
provide a match at additional function detector 142 is received, a
TV camera will be activated and the picture signal from the camera
will be transmitted to the central station as indicated in block
146. In a cable TV system, this transmission can be on the cable on
a frequency reserved for such feedback from the subscribers, or can
be on the same frequency as the central transmitter, which can be
turned off during the receipt of this requested camera frame. The
central station can relay this frame to the proper destination by,
in some cases, merely transmitting the address code of the
destination as the frame begins. Alternatively, the central station
can record the image in either analog or digitized form for
transmission to the destination at a later time. Thus within the
parameters discussed earlier, that is 600 users, this system could
provided pictures updated as often as once every 10 seconds from
each of 600 sites and might be used in a picturephone or mail
delivery system which provided pictures of the sender or of some
item whose image the sender wished to transmit.
The picturephone and mail delivery systems may be further described
by referring, first, to FIG. 6, which shows a neighborhood
picturephone system. The equipment within block 650 is located with
one subscriber, and the equipment within block 652 is located with
a different subscriber. Each subscriber has an address detector,
620 and 640, respectively, that functions as the TV receiver 34 and
address detector 42 of FIG. 1, the address detector being organized
as shown in FIG. 5. As shown in FIG. 1, the receiver 34 may receive
its signals via a cable, and so the address detectors 620 and 640
are connected to the same TV distribution cable 602. The display
622 and 642, respectively, functions as the video recorder 40 and
TV screen 2 of FIG. 1.
By way of illustration, the first subscriber, with telephone 628,
wishes to call the second subscriber, with telephone 648. Telephone
628 is used as described above for telephone 6 of FIG. 1 to
establish communication with the computer 601. A special number,
for example 9, is dialed to tell the program 601 that it should not
send weather data as in the example used to illustrate operation
with the system of FIG. 1, but should, instead, serve this
particular subscriber with picturephone service until a
disconnection control number is received. The subscriber then dials
the video address of the party he wishes to call, as it will be
detected by address box 640. Conventional software is used to
receive these control numbers, establish the references to the
proper subroutines, and store the video addresses of both parties
for subsequent use by the subroutines. The subscriber then uses
conventional telephone-company procedures for establishing a
conference-call circuit 660 for interconnecting his telephone 628
with telephone 648 of the party he wishes to call and with the
computer 601.
When this connection is established, the parties can converse by
telephone in the normal manner, but can also dial control numbers
into the computer. One of the picturephone subroutines 603 will
interpret these control numbers to set the timing rate for
delivering picturephone service, as described subsequently. If the
customer is billed, by conventional billing software, only for
pictures actually transferred, then there will be no picture charge
until the customer, after perhaps some preliminary conversation,
dials a control number. He will then be charged only for the rate
of pictures actually transferred, which will depend on the rate he
requests, in combination with other traffic on the cable, as
determined by conventional time-sharing scheduling routines.
Although a conference-call circuit 660 is shown, the subscriber
could, instead, dial the timing rate that he desires when he first
requests the computer to process the video addresses of himself and
the called party. Then, when he hangs up, he merely telephones the
called party in the normal manner, without requesting a conference
call, and the picturephone program will already have been set up to
run as requested. If desired, the computer can be provided with
circuits to periodically sense for this subscriber's activity and
provide the requested service only when activity is occurring, as
described subsequently.
Now the timing-rate subroutine 603 indicates the desired rate to
the main timing routine 605. This routine provides, in a
conventional manner, the scheduling and initiation of the various
services that have been requested by different subscribers,
including the sending of general and special weather forecasts, and
the like, as described in connection with FIG. 1.
When it is time to service the subscriber at the initiating address
box 620, the timing routine 605 initiates the routine 607 to send
the receiver address. This routine operates, much as the equivalent
routine in FIG. 1, to send the video address control signal that
initiates action at the called subscriber, 640. Accordingly, just
as described in FIG. 1, the display 642 will record, and
subsequently continuously display, the TV picture that is placed on
the cable during the remainder of the scan time (field or frame
time). However, the computer does not send any such picture.
Instead, it immediately proceeds with routine 609 to send the
camera address. This routine operates just as routine 607, except
that it sends, on the very next TV scan line, the special address
for the first subscribers's TV camera 626. The computer then sends
no more signals on the cable for the remainder of the scan time.
The subscriber's address box 620 has been supplying synchronizing
signals on line 623 to the camera 626 so that the camera is ready
to scan during the desired scan time.
When the address circuits 620 receive the special camera address,
they operate as described in connection with FIG. 5, and, via line
621, activate the transmitter 624 for one scan time to place the
scene viewed by camera 626 on the cable 602. Since neither the
computer nor any other camera is transmitting on the cable during
this scan time, and since address detector 640 and display 642 have
already been turned on for this scan time, the picture from camera
626 is sent to display 642. Timing routine 605 will, then, during
the next scan time, or some subsequent scan time, initiate
subroutines 607 and 609 to send the appropriate addresses in the
reverse order, so that a return picture will be sent back from
camera 646 to display 622 in much the same way as described above.
If desired, a simple detector can be connected to cable 602 at the
computer 601 so that, using conventional techniques, a subroutine
can interrogate the detector during a given scan time to discover
whether or not the addressed camera did, in fact, transmit a signal
during that time. The result of this interrogation can then be used
by the timing routine 605 to determine whether the subscriber has
started using the circuit, whether he has requested a different
rate of service by periodically (manually or automatically)
disabling his camera, or whether he has terminated the service by
disabling the camera for longer than a normal period. In this
manner, any number of subscribers connected to the same cable can
participate in picturephone service at rates determined by the
instantaneous load on the cable. It is not even necessary that both
subscribers transmit on the same radio frequency channel, so long
as the computer sends all addressing controls to a given subscriber
on the channel over which the other subscriber will be
transmitting. Or, for example, the subscriber may have his address
decoder tuned to the computer frequency, while his recorder is
tuned to the camera frequency.
FIG. 7 shows how this system can be expanded to use two or more
cables to provide city-wide picturephone service. The system
functions as described in connection with FIG. 6, with timing
routine 705 and initiate subroutines 707 and 709, except that the
subroutines are provided with conventional means to allow them to
transmit their control signals on selected ones of two or more
cables, and an additional subroutine 708 is used in a conventional
manner to activiate the proper one of several transfer gates 734,
735 that are used, for example, to relay the signal that appears on
one RF channel of line B and re-transmit it on the proper RF
channel of line A during the required scan time.
The picturephone systems described in FIGS. 6 and 7 have assumed
that reception occurs concurrently with transmission. In some
applications, it is desired to send a message that need not arrive
until some later time. FIG. 8 shows such a "mail delivery"
application. In this application, the computer has associated with
it a high-capacity recorder 822 such as a video disc recorder or a
conventional system for digitizing video signals and storing them
in computer bulk storage. The computer program has conventional
routines 807 and 817 for controlling the recorder so that the
computer can request the data on any given channel of any given
cable or line 802 during a given TV scan time to be recorded on an
addressed track or portion of the recorder 822, and so that it can
subsequently also request the data on that same portion of the
recorder to be played back on any given channel of any given line
804 during a given TV scan time.
To send a frame of "mail", a subscriber having equipment 650 of
FIG. 6 dials the computer, dials the control digit, for example
"8", that requests the timing and control program 805 of FIG. 8 to
activate the mail subroutines, and then dials the video address of
the intended recipient. Subroutine 805 then uses conventional
storage-management techniques to find a vacant portion of recorder
822, enter into the subroutine's storage-management tables the
destination-address now being assigned to this portion of the
recorder, and then, when time is available, activate subroutine 807
to enable the recorder to record, on that portion, the next
scan-time of data received on the channel and line 802 being used
by the originating subscriber. Subroutine 809 then, as described
for the equivalent subroutine 609 of FIG. 6, immediately sends the
camera address of the originating subscriber so that one scan of
data from his camera is placed on the cable, line 802.
Consequently, the originating subscriber transmits one scene, such
as a photograph, sketch, note, fingerprint, or other material that
then becomes recorded on one portion of recorder 822 and identified
with the recipient's video address via the storage-management
tables.
If he wishes, the subscriber may then dial a number that indicates
how long this data is to be saved before being destroyed.
Otherwise, it will be saved for a standard period of time
established for the system. Routine 805 uses conventional
techniques to enter the duration desired, bill the subscriber
accordingly, and destroy the data when time is up. At any time
before expiration of this interval, the intended recipient may
operate his equipment exactly as described in FIG. 1 except that
instead of dialing a request for weather information, he dials "8"
to request mail service, and then a "delivery" digit, for example
"1", which indicates that he wishes to receive, not send, mail.
Routine 805 then uses conventional techniques to consult its
storage-management tables to discover what portion of recorder 822
contains data for this destination.
Subroutines 817 and 819 then operate in a way similar to 22 and 28
of FIG. 1 to transmit that scan from the recorder 822 to the
subseriber's recorder and screen. And so in this manner, one frame
of "mail" can be sent from one subscriber to another. When the
receiving subscriber has seen this one frame, he may then dial "1"
again, which indicates to subroutine 805 that the
currently-selected frame is to be destroyed, and the next one is to
be found and sent. Or he may hang up, indicating to subroutine 805
that the currently-selected frame is to be destroyed, but the
status of all other waiting frames is not to be altered. Or he may
dial some other digit that indicates to subroutine 805 that he now
wishes to be billed for saving this frame for a period of time
indicated by the number he has dialed, instead of having it
destroyed by a subsequent dial of "1", or a hanging up. Subroutine
805 may use conventional techniques for identifying this saved
frame for later recovery by using a code number assigned by either
the subscriber or the subroutine. The subscriber may use this
feature to build up his own file of data from mail received from
elsewhere or that he sends "to himself". The subscriber may call
for the frames of his mail, or from any other file, one at a time
and record them on sequential parts of his own tape recorder. He
can also plug in the output of his recorder, in place of his
camera, to send to other subscribers, or to his own file in the
computer, selected frames from prerecorded tape, from tape recorded
"off the air", or tape used for capturing frames addressed to
him.
Although particular embodiments of picturephone and mail service
have been described, other methods of providing such service are
within the scope of the present invention. For example: One-way
picturephone or mail can occur between a station that has a camera
but no recorder, and one that has a recorder but no camera. Any
subscriber can switch his recorder and camera, separately, to any
RF channel of any cable at his location under the direction of the
computer, or according to some other procedure, in order to
maximize the utility of the service to all subscribers or in order
to accomplish some other purpose. Conventional privacy techniques,
such as the use of secret code numbers or electronic scrambling,
can be sued to avoid unauthorized access to, or destruction of,
mail or other data. In particular, for example, instead of
destroying a piece of mail on receipt of a simple signal, it might
be desirable to have billing for a frame transferred to the
recipient as soon as he sees that frame, and he will then be billed
for saving that frame indefinitely until he follows some specific
procedure for destroying it, such as dialing his own secret
authorization code. The examples have shown use of a single
computer, but conventional techniques could be used for
interconnecting computers at distant locations and routing traffic
to, or through, them to form a transcontinental, or larger,
picturephone and mail system. Use of cables has been described
here, but the system will also work for broadcasting through air or
space if the subscribers with cameras are properly licensed, and if
the computer makes proper allowances for any anticipated time
delays such as those encountered on earth-moon, or even shorter,
communications.
The additional function detector can also be used to set
electronically the address selection switches of the user's generic
address detector or specific address detector. Thus the system has
tremendous inherent capability permitting interactions between the
user and the central computer installation, and, if desired,
between users. Individual users can be granted the power to force
specific addresses upon other users through the use of the other
users' additional function detector used as described above in
connection with the cascaded address.
While the system of FIG. 1 was described in conjunction with a
video disc recorder, block 30, the video information, as well as
address information, can be stored in any other means, including
means such as conventional core storage or bulk digital storage. If
digital storage is utilized, each TV frame in storage can be a
precoded frame originally coded to include the TV scan line address
in binary code, the column address in binary code, and the text
characters in ASCII American Standard Code for Information
Interchange) code for each row of text characters to display. It
can also be originally coded to include a place for the
subscriber's address code by making the first such text row an "all
zeros" TV address. This can consist of the ASCII characters for
"space", "dash" and "eight spaces" written on a white background as
the first 10 characters of a row before the text of the frame. The
precoded frame can also include a similar row of "disconnect" data
(with the same ASCII characters) to be transmitted after the text
of the frame. For reasons discussed below, the remainder of the
frame does not include any characters in the first two columns of
any row. However, before the frame is transmitted, the computer
installation software will insert the subscriber's TV address by
using conventional techniques to, first, convert the string of
eight binary digits of the TV address to a string of eight ASCII
characters in which each zero is represented by ASCII "space", and
each ONE by ASCII "dash", and, second, insert this string of
characters into the frame in place of the eight spaces of the
above-mentioned precoded all zeros subscriber's TV address, whose
core location is determined in a conventional manner from a
relative address that has been precoded in the frame as part of its
auxiliary control data.
At this point, the frame, in core storage, is ready to transmit,
and so the computer software causes it to be read out to a
conventional commercially available television display system
(TDS). Conventional output program routines perform this read-out.
The TDS system may be any conventional system such as the Model
6600 disc controlled system manufactured by Data Disc Inc.
The TV frame is coded as set forth above for the following reasons:
First, since no rows (except the two special ones above), contain
characters in the first two columns, none of their scan lines will
contain a control flag as specified in waveform a of FIG. 3 for
addresses, since each column corresponds to a single 0.8
microsecond address-bit position in waveform a of FIG. 3. Second,
on the two special rows that contain spaces and dashes on the white
background, all the scan lines will be all white for the first 10
columns except for the one line that actually contains the "dash"
mark, and so these all white lines also contain no control flag.
Third, the "dash" marks will occur on only one scan line of the
row. Fourth, for a scan line that contains the "dash" marks, the
video signal will appear as in waveform a of FIG. 3, with each
blank causing a "white" level and then each "dash" causing a
"black" level. Fifth, the "subscriber's TV address" row will be
sent, decoded by the subscriber's equipment as discussed in
connection with FIG. 4, and used to start his recorder. Then the
text will be transmitted and recorded, and, finally, the
"disconnect" row will be sent, which (because of its control flag
followed by all white) will be interpreted by the subscriber's
equipment as not his address (because in this example, it is
assumed that no subscriber will use an all white address code), and
will cause recording to stop.
This process occurs during only one field of an interlaced frame,
and, therefore, consists of only odd numbered lines or only even
numbered lines. A conventional type I standard tape recorder
typically will record all fields it receives, but, in frame-freeze
playback, shows only one field on both the odd and even lines.
Consequently, if only one field is addressed to a recorder, it will
be recorded regardless of whether it is an "odd" or "even" field.
Alternatively, some types of recorders record only one of each pair
of fields it receives, and so for these recorders, the computer can
send the same addressed field twice to assure that at least one of
them will be recorded.
While particular operating modes have been described above, any of
a variety of start-stop sequences may be utilized. For example,
automatic cessation after writing one row, one field or one frame
may be utilized. In this case, if a user is to record a longer
interval than that in the automatic cessation program, more
transmissions of the subscriber's address code must be generated,
but a disconnect code need not be generated and sent. As another
example, if in the system described above, a different subscriber's
address code will be sent in time or a repeated transmission of the
subscriber's frame is to occur, a disconnect code need not be
sent.
Those skilled in communications techniques will recognize that
following the teachings of the present invention a variety of
methods may be utilized to generate single or multiple
cascaded-address control codes for controlling cascade dependent
subscriber's controls so that, for example, a group of special
signals can be generated and sent at the start of any frame for
presetting the control circuits of one or more specific subscribers
to be receptive to certain frame address codes that will be sent
for the same or subsequent one or more frames. Similarly, as
indicated above, a subscriber, himself, can influence not only
frames subsequently sent to him but frames to be stored or sent to
other subscribers.
While several specific illustrative examples have been set forth
above, those skilled in relevant arts will recognize that
variations can be made without departing from the scope of the
present invention. Similarly, while some of the described
embodiments assume that the subscriber has equipment of the type
presently coming on the market with home video recorders, the
provision of the indicated connections for video inputs and outputs
may be easily added by the ordinary television serviceman to any
present-day television receiver.
* * * * *